Sub-cooling unit for cooling system and method

ABSTRACT

A system for cooling a medium includes a line having coolant flowing therein, and a sub-cooling unit in fluid communication with the line. The sub-cooling unit receives a portion of the coolant diverted from the line to cool coolant flowing in the line. A method of cooling a medium is further disclosed.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/243,628, filed Oct. 5, 2005, entitled SUB-COOLING UNIT FOR COOLINGSYSTEM AND METHOD, now U.S. Pat. No. 7,406,839, each of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to cooling systems, and more particularlyto cooling systems used with racks and enclosures used for dataprocessing, networking and telecommunications equipment.

2. Discussion of Related Arts

Communications and information technology equipment is commonly designedfor mounting on racks and for housing within enclosures (often includedin the term “rack”). Equipment racks are used to contain and to arrangecommunications and information technology equipment, such as servers,CPUs, data processing equipment, networking equipment,telecommunications equipment and storage devices, in relatively smallwiring closets as well as equipment rooms and large data centers. Anequipment rack can be an open configuration or can be housed within arack enclosure, although the enclosure may be included when referring toa rack. A standard rack typically includes front-mounting rails to whichmultiple units of equipment, such as servers and CPUs, are mounted andstacked vertically, for example, within the rack. A standard rack at anygiven time can be sparsely or densely populated with a variety ofdifferent components (e.g., server blades) as well as with componentsfrom different manufacturers.

Most rack-mounted communication and information technology equipmentconsumes electrical power and generates heat, which can have an adverseeffect on the performance, reliability and useful life of the equipmentcomponents. In particular, rack-mounted equipment housed within anenclosure is particularly vulnerable to heat build-up and hot spotsproduced within the confines of the enclosure during operation. Theamount of heat generated by a rack of equipment is dependent on theamount of electrical power drawn by equipment in the rack duringoperation. The amount of heat a given rack or enclosure can generate,therefore, may vary considerably from a few tens of watts up to about40,000 watts, and this upper end continues to increase with the constantevolution of this technology.

In some embodiments, rack-mounted equipment is cooled by drawing airalong a front side or air inlet side of a rack, drawing air through itscomponents, and subsequently exhausting air from a rear or vent side ofthe rack. Airflow requirements to provide sufficient air for cooling canvary considerably as a result of different numbers and types ofrack-mounted components and different configurations of racks andenclosures.

Equipment rooms and data centers are typically equipped with an airconditioning or cooling system that supplies and circulates cool air toracks. One such cooling system employs a raised floor to facilitate airconditioning and circulation systems. Such systems typically use openfloor tiles and floor grills or vents to deliver cool air from an airpassageway disposed below the raised floor of an equipment room. Openfloor tiles and floor grills or vents are typically located in front ofequipment racks, and along aisles between rows of racks arrangedside-by-side.

One cooling system is disclosed in co-pending U.S. patent applicationSer. No. 10/993,329, entitled IT EQUIPMENT COOLING, filed on Nov. 19,2004, which is owned by the assignee of the present application and isincorporated herein by reference. In one embodiment, this systemincludes one or more main condensing modules, a coolant distributionsection, a heat exchanger module section, and a backup coolant section.The coolant distribution section includes a bulk storage tank, anevacuation/recovery pump, a manifold and hoses. The condensing module(s)sends cool liquid to the heat exchanger module section by means of thedistribution section, where the liquid is evaporated, into gas by hotair from the IT equipment, and the vapor coolant is returned to the maincondensing module(s). At the main condensing module(s), a primarycooling portion cools the heated vapor coolant back into a liquid forsupply to the heat exchanger module section by the distribution section.In the case of a failure of one of the primary condensing modules, asecondary condensing module can cool and condense the heated vaporcoolant if power has not failed to the system. If power has failed tothe system, the backup coolant section, which may include several icestorage tanks, can continue to cool, without using high powerconsumption vapor compression systems, the heated coolant from the heatexchange module section for the duration of battery life or depletion ofice storage of the system.

SUMMARY OF THE INVENTION

One aspect of the invention is directed to a system for cooling amedium. In one embodiment, the system comprises a line having coolantflowing therein, and a sub-cooling unit in fluid communication with theline. The sub-cooling unit receives a portion of the coolant divertedfrom the line to cool coolant flowing in the line.

Embodiments of the system may include the sub-cooling unit comprising asub-cooling expansion device in fluid communication with the line, asub-cooling heat exchanger, in fluid communication with the sub-coolingexpansion device, to absorb heat from the coolant flowing in the line,and a sub-cooling pump, in fluid communication with the sub-cooling heatexchanger, to pump the portion of diverted coolant to the line. In oneembodiment, the sub-cooling heat exchanger comprises a co-axialcondensing unit in fluid communication with the line and the sub-coolingunit. In one embodiment, the portion of coolant diverted to thesub-cooling unit is less than 5% of the liquid coolant flowing throughthe line. In a particular embodiment, the portion of coolant diverted tothe sub-cooling unit is approximately 2% of the liquid coolant flowingthrough the line. The system may comprise a condensing unit, in fluidcommunication with the line, adapted to cool coolant from asubstantially vaporized state to a substantially liquid state, and amain pump, in fluid communication with the condensing unit by the line,adapted to pump coolant in liquid state. The system may further comprisea controller to control the operation of the cooling system. Thecontroller controls the portion of coolant diverted from the lineconnecting the condensing unit to the main pump.

Another aspect of the invention is directed to a system for cooling amedium, the system comprising a line having coolant flowing therein, andmeans for cooling the coolant flowing through the line by diverting aportion of coolant from the line and absorbing heat from the coolantflowing through the line with the portion of diverted coolant.

In certain embodiments, the means for cooling the coolant flowingthrough the line comprises a sub-cooling unit, in fluid communicationwith the line, the sub-cooling unit receiving the portion of the coolantdiverted from the line. The sub-cooling unit comprises a sub-coolingexpansion device in fluid communication with the line, a sub-coolingheat exchanger, in fluid communication with the sub-cooling expansiondevice, to absorb heat from the coolant flowing in the line, and asub-cooling pump, in fluid communication with the sub-cooling heatexchanger, to pump the portion of diverted coolant to the line. Thesub-cooling heat exchanger comprises a co-axial condensing unit in fluidcommunication with the line and the sub-cooling unit. The system furthercomprises a condensing unit, in fluid communication with the line,adapted to cool coolant from a substantially vaporized state to asubstantially liquid state, and a main pump, in fluid communication withthe condensing unit via the line, adapted to pump coolant in liquidstate. The system may further comprise a controller to control theoperation of the cooling system, wherein the controller controls theportion of coolant diverted from the line connecting the condensing unitto the main pump. In one embodiment, the portion of coolant diverted tothe sub-cooling unit is less than 5% of the liquid coolant flowingthrough the line. In a particular embodiment, the portion of coolantdiverted to the sub-cooling unit is approximately 2% of the liquidcoolant flowing through the line.

A further aspect of the invention is directed to a method of coolingcoolant within a line. The method comprises diverting a portion ofcoolant flowing through the line to a sub-cooling unit, and absorbingheat from the coolant flowing through the line with the portion ofcoolant diverted to the sub-cooling unit.

Embodiments of the method may further comprise pumping the portion ofcoolant back to the line. In one embodiment, the portion of coolantdiverted to the sub-cooling unit is less than 5% of the coolant flowingthrough the line. In a particular embodiment, the portion of coolantdiverted to the sub-cooling unit is approximately 2% of the coolantflowing through the line.

Yet another aspect of the invention is directed to a cooling systemcomprising a condensing unit adapted to cool coolant from asubstantially vaporized state to a substantially liquid state. Thesystem further includes a main pump, in fluid communication with thecondensing unit, adapted to pump coolant, and a sub-cooling unit influid communication with the condensing unit. The sub-cooling unitreceives a portion of coolant diverted from the condensing unit to themain pump to cool the coolant flowing from the condensing unit the mainpump.

Embodiments of the invention may include the sub-cooling unit comprisinga sub-cooling expansion device in fluid communication with thecondensing unit, a sub-cooling heat exchanger, in fluid communicationwith the sub-cooling expansion device, adapted to absorb heat fromcoolant flowing from the condensing unit to the main pump, and asub-cooling pump, in fluid communication with the sub-cooling heatexchanger and the condensing unit, adapted to pump the diverted coolantback to the condensing unit. The sub-cooling heat exchanger comprises aco-axial condensing unit in fluid communication with the condensing unitand the sub-cooling unit. The system may further include a controller tocontrol the operation of the cooling system, wherein the controllercontrols the portion of coolant diverted from the condensing unit to themain pump. In one embodiment, the portion of coolant diverted to thesub-cooling unit is less than 5% of the liquid coolant flowing from thecondensing unit to the main pump. In a particular embodiment, theportion of coolant diverted to the sub-cooling unit is approximately 2%of the liquid coolant flowing from the condensing unit to the main pump.

The present invention will be more fully understood after a review ofthe following figures, detailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference is madeto the figures which are incorporated herein by reference and in which:

FIG. 1 is a schematic representation of a system for cooling anenclosure or rack having a sub-cooling unit of an embodiment of theinvention for cooling coolant flowing from a condensing unit to a pump;and

FIG. 2 is a flow diagram of a method of an embodiment of the inventionfor sub-cooling coolant of a cooling system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of illustration only, and not to limit the generality,the present invention will now be described in detail with reference tothe accompanying figures. This invention is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in thedrawings. The invention is capable of other embodiments and of beingpracticed or being carried out in various ways. Also the phraseology andterminology used herein is for the purpose of description and should notbe regarded as limiting. The use of “including,” “comprising,” “having,”“containing” “involving,” and variations thereof herein, is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items.

Referring to the drawings, and more particularly to FIG. 1, there isgenerally indicated at 10 a system for cooling a space containing, forexample, electronic equipment, including closets, equipment rooms anddata centers. Such spaces are adapted to house enclosures or racksdesigned to house networking, telecommunication and other electronicequipment. In one embodiment, the cooling system 10 may be employed inthe type of cooling system disclosed in U.S. patent application Ser. No.10/993,329, entitled IT EQUIPMENT COOLING, filed on Nov. 19, 2004, whichis referenced above and incorporated herein by reference. As discussedin greater detail below, the cooling system 10 of embodiments of thepresent invention is designed to improve the efficiency and reliabilityof the entire cooling system by diverting a portion of coolant from acondensing unit to a pump to further sub-cool the coolant beingdelivered to the pump.

As shown in FIG. 1, a medium or coolant, such as but not limited toR134A and R410A coolants, is provided within a closed system comprisinga main pump 12, which is designed to pump liquid coolant. The liquidcoolant is disposed within the closed system under increased pressureprovided by the main pump 12. In one embodiment, the main pump 12 mayembody two centrifugal pumps placed in series, which are capable ofincreasing the overall pressure of the coolant between 20-25 psig, forexample. In this embodiment, the pumps may be of the type sold by TarkIncorporated of Dayton, Ohio, under model no. WRD40.5A-23. However, asingle pump capable of achieving an overall pressure increase of 20-25psig may be provided and still fall within the scope of the presentinvention.

The main pump 12 delivers the liquid coolant under increased pressure toan expansion valve 14, which is in fluid communication with the mainpump via line 16. The expansion valve 14 conditions the coolant so thatthe coolant experiences a slight pressure and temperature drop afterflowing through the expansion valve. In one embodiment, the expansionvalve 14 may be of the type sold by the Sporlan Division ofParker-Hannifin Corporation of Washington, Mo., under model no.OJE-9-C-⅝″-⅝″ ODF-5′.

Once through the expansion valve 14, the coolant, in a form of lowpressure liquid/vapor mix (80% liquid and 20% vapor), flows through atleast one evaporator unit 18 in fluid communication with the expansionvalve 14 via line 20. In one embodiment, the evaporator unit 18 may takethe form of a tubular coil having fins that are adapted to absorb heatfrom a space, such as hot air taken from the aforementioned closet,equipment room or data center. Such an evaporator unit 18 may be amicro-channel evaporator having two rows, 25.4 mm micro-channel coilassembly that is manufactured by and commercially available fromHeatcraft of Grenada, Miss. In other embodiments, the evaporator unitmay be adapted to absorb heat from another medium, such as heatedcoolant delivered to the evaporator unit, in which the heated mediumcontains heat taken from the space requiring cooling.

As shown in FIG. 1, a heat load 22 from the space requiring cooling isapplied to the evaporator unit 18. The heat from the heat load 22, whichmay be in the form of warm air directed by fans from equipmentenclosures at the evaporator unit 18, vaporizes the slightlyreduced-pressure coolant traveling through the evaporator unit. Thus,the temperature of the vapor coolant flowing within the evaporator unit18 is greater than the temperature of the low pressure liquid/vapor mixentering the inlet of the evaporator unit via line 20. Although thetemperature is greater, the resultant pressure of the vapor coolantexiting the evaporator unit 18 is substantially equal to the pressure ofthe low pressure liquid/vapor mix.

The vapor coolant, which is in super heated condition, flows underrelatively low pressure to a condensing unit 24, such as a condensingunit manufactured by WTT America, Inc. of Bohemia, N.Y. under model no.WTT W9-130. As shown, the condensing unit 24 is in fluid communicationwith the evaporator unit 18 and the main pump 12 via lines 26, 28,respectively. It should be noted that the super heated vapor coolantdischarged from the evaporator unit 18 and traveling to the condensingunit 24 experiences a slight pressure loss in line 26. The condensingunit 24 is designed to cool the super heated vapor coolant entering thecondensing unit and return the cooled coolant in a liquid state to themain pump 12 via line 28. As discussed above, given the design of themain pump 12, a requirement of the cooling system 10 is that coolantentering the main pump be in a liquid state.

In one embodiment, coolant requiring cooling within the condensing unit24 may be subjected to a heat exchanger 30 in the form of a chillingunit, which is adapted to provide chilled water (e.g., approximately 45°F. water) in direct fluid communication with the condensing unit vialines 32, 34. The arrangement is such that chilled water entering thecondensing unit 24 via line 34 cools the vaporized coolant to a liquidstate. Warmer water (e.g., approximately 52° F. water) flows back to achiller plant via line 32 for further cooling. Liquid coolant is thendirected from the condensing unit 24 to the main pump 12, where thecycle of pumping, expanding, heating and cooling the coolant beginsagain.

A controller 36, such as the controller disclosed in theabove-referenced patent application Ser. No. 10/993,329, is configuredto control the operation of the cooling system 10 illustrated in FIG. 1.The main pump inlet conditions at line 28 are critical in two-phasepumped coolant systems because liquid pumps, such as main pump 12,require 100% liquid. To run efficiently, and to prevent failure of themain pump 12, sub-cooled liquid coolant is desirable. Specifically, asthe condensing unit 24 cools vapor coolant via the heat exchanger 30,and “acceptable” liquid coolant (coolant that is sufficiently cooled toliquid phase) is directed to the main pump 12, the acceptable coolantmay not be sufficiently cooled for the main pump to operate properly.Stated another way, it is desirable for all of the coolant entering themain pump 12 be in a liquid state. Otherwise, cavitation and/or vaporlock may result in the incapacitation of the main pump 12. Failure ofthe main pump 12 may result in the catastrophic failure of the coolingsystem 10, thereby jeopardizing the continued operation of theelectronic equipment requiring cooling.

Often, due to environmental conditions, for example, it is difficult tocool coolant within the outlet of the condensing unit 24 to atemperature sufficient to ensure that the coolant is in a liquid stateprior to its delivery to the main pump. Since the temperature of theoutlet of the condensing unit 24 within line 28 is near the temperatureof the coolant requiring further cooling by the heat exchanger, there issometimes a need to further sub-cool the coolant to ensure that 100% ofthe coolant delivered to the main pump 12 is in liquid state. One way toachieve this lower temperature is to provide a separate cooling system,e.g., water chillers, in conjunction with another, oversized condensingunit. However, such approaches are expensive to install and operate, andare not practical in most applications.

Still referring to FIG. 1, there is illustrated the cooling system 10with a sub-cooling unit, generally indicated at 40, of an embodiment ofthe present invention. As shown, the sub-cooling unit 40 is disposedgenerally between the condensing unit 24 and the main pump 12 so that itis in fluid communication with these components of the cooling system 10in the manner described below. Specifically, as described above, coolantcooled by the condensing unit 24 is directed to the main pump 12 vialine 28. With embodiments of the present invention, a small portion ofthe coolant is diverted by line 42 to the sub-cooling unit 40 forfurther cooling. In some embodiments, the mass of coolant diverted toline 42 is less than 5% of the total mass of coolant delivered to themain pump 12 from the condensing unit 24. In a preferred embodiment, themass of coolant diverted to line 42 from the main pump 12 isapproximately 2% of the total mass of coolant delivered.

The controller 36, which is in electrical communication with a valve at44, may be configured to determine the amount of coolant diverted basedon the environmental conditions of the coolant at the main pump 12 andwithin the sub-cooling unit 40. The remaining coolant, i.e., thenon-diverted coolant, continues to flow to the main pump 12 via line 28.As will be described in greater detail below, the coolant delivered tothe main pump 12 is cooled to a sufficiently cool temperature (dependingon the type of coolant employed and the environmental conditionsimpacting the cooling system 10) to ensure the coolant is in a liquidstate.

Before being diverted, the coolant flows from the condensing unit 24through a heat exchanger 46 disposed between the condensing unit 24 andthe main pump 12. In one embodiment, the heat exchanger 46 comprises aco-axial condensing unit having concentric tubes. The arrangement issuch that coolant exiting the condensing unit 24 via line 28 flowswithin an inner tube (not shown) of the co-axial condensing unit 46 andcoolant diverted to line 42 flows within an outer tube (not shown) ofthe co-axial condensing unit that houses the inner tube therein.Co-axial condensing units are well known in the art, and may be of thetype offered by Packless Industries of Waco, Tex. under model no.AES003522. As discussed in greater detail below, it is within thisco-axial condensing unit 46 that the coolant flowing from the condensingunit 24 to the main pump 12 by line 28 is cooled by the coolant divertedto the sub-cooling unit 40.

As shown in FIG. 1, the sub-cooling unit 40 includes a sub-coolingexpansion valve 48 connected to line 42 to reduce the pressure and thetemperature of the coolant diverted to the sub-cooling unit. In someembodiments, the sub-cooling expansion valve 48 may be replaced by acapillary tube or restrictive orifice. In one embodiment, thesub-cooling expansion valve may be of the type sold by the SporlanDivision of Parker-Hannifin Corporation of Washington, Mo., under the SJseries of expansion valves.

As stated above, the heat exchanger 46 (i.e., the co-axial condensingunit) receives coolant from the sub-cooling expansion valve 48 via line52, so that the coolant flowing through the outer tube absorbs heat fromthe coolant flowing through the inner tube. It is at this point wherethe coolant directed to the main pump 12 via line 28 is sub-cooled bythe sub-cooling unit 40. A sub-cooling pump 54 is in fluid communicationwith the sub-cooling heat exchanger 46 and the condensing unit 24 vialines 56, 58, respectively, to pump the diverted coolant back to thecondensing unit.

In summary, “acceptable” liquid coolant is directed from the condensingunit 24 to the main pump 12 via line 28. The valve 44, undermanipulation of the controller 36, diverts a small portion of the massof coolant to the components of the sub-cooling unit 40. The valve 44may be configured to direct a select amount of coolant to thesub-cooling unit by the controller. For example, 2% of the total mass ofcoolant traveling to the main pump by line 28 may be diverted to thesub-cooling unit 40. The diverted coolant is expanded by the sub-coolingexpansion valve 48, which significantly reduces the pressure and thetemperature of the coolant. The sub-cooling heat exchanger 46 isdesigned to remove heat from the coolant in line 28 directed to the mainpump 12 with the diverted sub-cooled coolant thereby ensuring that thecoolant being directed to the main pump is in a liquid state.

Once heated by the heat exchanger 46, the vaporized coolant ispressurized by the liquid/vapor sub-cooling pump 54, which is in fluidcommunication with the sub-cooling heat exchanger and the condensingunit 24 via lines 56, 58, respectively. At this point, the pressure ofthe vaporized coolant is low, thereby requiring the provision ofsub-cooling pump 54 to pressurize the coolant to a pressure sufficientfor reintroduction into the line 26 carrying coolant from theevaporator(s) unit 18. Specifically, the liquid/vapor coolant isprovided under pressure within line 58 and travels to line 26 where itis introduced back into the vaporized coolant traveling from theevaporator unit(s) 18. In one embodiment, the liquid/vapor pump 54 is alinear piston pump manufactured by Pumpworks Inc. of Minneapolis, Minn.The pressure of liquid/vapor coolant within line 58 is substantiallysimilar to the pressure of vapor coolant in line 26, and once introducedback into line 26, the coolant travels to the condensing unit 24.

Thus, it should be observed that the sub-cooling unit 40 of the presentinvention may be employed in any one of the condensing units shown anddescribed in the cooling system disclosed in U.S. patent applicationSer. No. 10/993,329, entitled IT EQUIPMENT COOLING. The sub-cooling unit40 is particularly effective in ensuring that coolant delivered to apump is in a liquid state. The sub-cooling unit 40 relies on coolantwithin the closed system to sub-cool the coolant that is delivered to amain pump.

Turning now to FIG. 2, a method of sub-cooling coolant within a coolingsystem, such as cooling system 10, is generally indicated at 70. At 72,coolant is pumped to an expansion device, such as expansion valve 14, bya pump, such as main pump 12. At 74, the expansion device expands thecoolant so that the coolant is conditioned to receive a heat load. At76, the heat load is applied to the coolant, the heat load being appliedfrom a space requiring cooling, such as a space accommodating electronicequipment. The heat load applied to the coolant is typically sufficientto vaporize the coolant. Next, at 78, the coolant is condensed to aliquid state and directed back to the pump, where the cycle beginsagain.

Still referring to FIG. 2, at 80, a portion of coolant is diverted to asub-cooling unit, such as sub-cooling unit 40, which is designed tosub-cool coolant flowing to the pump. The method of the presentinvention may divert a select amount of coolant, e.g., 2% of the coolantflowing to the main pump based on environmental conditions of thecoolant exiting the condensing unit. At 82, the portion of divertedcoolant enters a heat exchanger (e.g., heat exchanger 46) to absorb heatfrom the coolant traveling to the pump. The heat absorbed by the heatexchanger results in the further cooling of the coolant flowing to thepump. After absorbing heat of the coolant, the diverted portion ofcoolant is pumped back to the condensing unit at 84, which cools theliquid/vapor coolant.

It should be observed that the sub-cooling unit 40 of embodiments of thepresent invention may be used cooling systems other than the coolingsystem 10 illustrated in FIG. 1. The sub-cooling unit 40 may be employedin any system, whether a cooling or heating system, having a pumpdesigned to pump liquid coolant. The provision of the sub-cooling unit40 enables such systems to operate efficiently and more reliably.

Having thus described at least one embodiment of the present invention,various alternations, modifications and improvements will readily occurto those skilled in the art. Such alterations, modifications andimprovements are intended to be within the scope and spirit of theinvention. Accordingly, the foregoing description is by way of exampleonly and is not intended to be limiting. The invention's limit isdefined only in the following claims and equivalents thereto.

1. A method of cooling coolant in a system, the method comprising:delivering coolant in a substantially vaporized state to a condensingunit; cooling coolant from the substantially vaporized state to asubstantially liquid state; delivering the coolant in the substantiallyliquid state to a pump within a line; diverting a portion of coolantflowing through the line from the pump to a sub-cooling unit comprisinga sub-cooling expansion device and a sub-cooling heat exchanger;absorbing heat from the coolant flowing through the line with theportion of vaporized coolant diverted to the sub-cooling unit with thesub-cooling heat exchanger, and returning the diverted vaporized coolantto the condensing unit by a vapor pump.
 2. The method of claim 1,wherein the portion of coolant diverted to the sub-cooling unit is lessthan 5% of the coolant flowing through the line.
 3. The method of claim1, wherein the portion of coolant diverted to the sub-cooling unit isapproximately 2% of the coolant flowing through the line.
 4. The methodof claim 1, further comprising controlling an amount of coolant divertedfrom the pump to the sub-cooling unit.